1. Field of the Invention
This invention relates generally to agricultural equipment and more particularly to an improved knock down wheel construction for agricultural apparatus such as so-called wheel-move irrigation pipe lines.
2. Prior Art
As will appear from the ensuing description, the improved agricultural wheel construction of the invention may be used on a variety of agricultural machines. The wheel construction, however, is intended primarily for so-called wheel-move irrigation pipe lines and will be described in this context.
Wheel-move irrigation pipe lines are well known and widely used in agriculture and hence need not be described in elaborate detail. Simply described, a wheel-move irrigation pipe line comprises a long (e.g., quarter mile) irrigation line composed of pipe sections coupled end to end and supported at intervals by wheels surrounding the pipe. Each wheel has a central hub through which the pipe extends, whereby the irrigation pipe line may roll across the field from one irrigating position to another. A power means is provided for driving the wheels, or turning the pipe, to propel the wheel line in its rolling movement. Mounted on the irrigation pipe at intervals therealong are irrigation sprinklers, such as the well known impulse or Rainbird sprinklers which receive water through the pipe. The detailed construction and mode of operation of such apparatus is disclosed in my U.S. Pat. No. 3,147,764.
In operation of such an irrigation pipe line, the pipe must be located at a sufficient elevation above the ground to clear the fully grown crops in the crop rows or at least avoid damaging contact with the crops. This required elevation of the irrigation pipe, in turn, determines the diameter of the pipe line wheels since the wheels must have a radius equal to the required pipe elevation. As a consequence, irrigation pipe line wheels are often quite large in diameter and, in some cases, may have a diameter on the order of 12 to 14 feet or more. Because of this large diameter, the weight and strength of the wheels are critical factors in the design of such an irrigation pipe line. Thus, the wheels must possess sufficient strength and rigidity not only to support their own dead weight and that of the water loaded irrigation pipe when stationary during irrigation but, also, to resist the torsion and bending loads to which the wheels are subjected during rolling of the line from one location to the other. On the other hand, the wheels, as well as the other components of an irrigation pipe line, must be sufficiently light to enable the pipe line to be shipped to and handled and assembled by the user.
Further, because of their relatively large size, irrigation pipe line wheels of the kind under discussion, cannot be conveniently shipped in their assembled condition. As a consequence, such wheels must be designed for shipment in a knocked down or disassembled condition and for subsequent assembly by the user. The assembly procedure should be relatively simple and quick to accomplish and capable of accomplishment without the use of special tools. Also, of course, the wheels should be relatively economical to manufacture, simple in construction, and reliable in operation.
Irrigation pipe line wheels of this general kind, of course, have been devised. One such wheel construction, for example, is described in my prior U.S. Pat. No. 3,218,105. Because of the necessity of satisfying the above requirements, most of the existing irrigation pipe line wheels, as well as that of the present invention, are spoked wheels having a hub, an annular ring-like rim surrounding the hub, and spokes extending between and joining the rim and the hub. In my aforementioned patent, the spokes are bolted to the hub and rim and the rim is constructed in sections bolted to one another such that the wheel may be shipped in a knock down or disassembled condition and then reassembled at the point of use.